linux-kernel - [PATCH 3/5] accel/qaic: Flush the transfer list again

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Date:   Wed, 17 May 2023 13:35:38 -0600
From:   Jeffrey Hugo <quic_jhugo@...cinc.com>
To:     <ogabbay@...nel.org>, <jacek.lawrynowicz@...ux.intel.com>,
        <quic_pkanojiy@...cinc.com>, <stanislaw.gruszka@...ux.intel.com>,
        <quic_carlv@...cinc.com>, <quic_ajitpals@...cinc.com>
CC:     <linux-arm-msm@...r.kernel.org>, <dri-devel@...ts.freedesktop.org>,
        <linux-kernel@...r.kernel.org>,
        Jeffrey Hugo <quic_jhugo@...cinc.com>
Subject: [PATCH 3/5] accel/qaic: Flush the transfer list again

From: Pranjal Ramajor Asha Kanojiya <quic_pkanojiy@...cinc.com>

Before calling synchronize_srcu() we clear the transfer list, this is to
allow all the QAIC_WAIT_BO callers to exit otherwise the system could
deadlock. There could be a corner case where more elements get added to
transfer list after we have flushed it. Re-flush the transfer list once
all the holders of dbc->ch_lock have completed execution i.e.
synchronize_srcu() is complete.

Fixes: ff13be830333 ("accel/qaic: Add datapath")
Signed-off-by: Pranjal Ramajor Asha Kanojiya <quic_pkanojiy@...cinc.com>
Reviewed-by: Carl Vanderlip <quic_carlv@...cinc.com>
Reviewed-by: Jeffrey Hugo <quic_jhugo@...cinc.com>
Signed-off-by: Jeffrey Hugo <quic_jhugo@...cinc.com>
---
 drivers/accel/qaic/qaic_data.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/accel/qaic/qaic_data.c b/drivers/accel/qaic/qaic_data.c
index 1285c3dc9aef..8603e99a2a61 100644
--- a/drivers/accel/qaic/qaic_data.c
+++ b/drivers/accel/qaic/qaic_data.c
@@ -1845,6 +1845,11 @@ void wakeup_dbc(struct qaic_device *qdev, u32 dbc_id)
 	dbc->usr = NULL;
 	empty_xfer_list(qdev, dbc);
 	synchronize_srcu(&dbc->ch_lock);
+	/*
+	 * Threads holding channel lock, may add more elements in the xfer_list.
+	 * Flush out these elements from xfer_list.
+	 */
+	empty_xfer_list(qdev, dbc);
 }
 
 void release_dbc(struct qaic_device *qdev, u32 dbc_id)
-- 
2.40.1